Dan Jennings, previously struck by liner, starts wearing cap insert

Chicago White Sox reliever Dan Jennings, one of a dozen active pitchers who have been hit in the head by a line drive, is the first publicly known to have started wearing protective padding after being struck.

"If it happened again and I wasn't wearing anything, I'd feel pretty stupid," Jennings said by phone Saturday.

The 28-year-old left-hander was with the Miami Marlins on Aug. 7 when he suffered a concussion on a 101 mph line drive off the bat of Pittsburgh's Jordy Mercer that hit him on the left temple. The ball ricocheted into the air and was caught by the shortstop for an out. The ballpark became silent as Jennings knelt unsteadily, but he stayed conscious and waved to a standing crowd while seated in a cart that took him off the field.

Dan Jennings, then of the Miami Marlins, after he was hit in the head by a ball on Aug. 7, 2014. AP Photo/Gene J. Puskar

Jennings said he saw last month's "Outside the Lines" report about pitchers' head protection and asked the White Sox equipment staff for the opportunity to try what is worn by Houston Astros righty Collin McHugh -- Safer Sports Technologies' SST Pro Performance Head Guard. Soon after, Jennings said, he began using the 1.6-ounce hard carbon fiber partial insert with Kevlar padding on the side where he got hit.

"I'm thrilled," said Matt Meier, founder and CEO of the Georgia-based company. "His well-documented incident is what we're trying to prevent."

Would the protective padding Jennings is now wearing have adequately protected him on the Mercer liner?

"Absolutely," the four-year veteran said. "I might have had a headache for a few days, but it's protection in the perfect spot where I was hit."

Major League Baseball and the MLB Players Association have not tested or approved the product, but Meier said when his company tested it at speeds in the low 90s, it took four or five such impacts before it started to crack.

MLB and the MLBPA have approved one product, and New York Mets reliever Alex Torres is the only pitcher to wear it. The thick 8-ounce isoBLOX foam padding goes around the outside of caps, and MLB officials said it was certified in independent testing against liners at 83 mph, determined to be the average speed of shots reaching the mound area.

Jennings' teammate Hector Noesi and the Yankees' Esmil Rogers use another padding, Unequal Technologies' 5½-ounce Dome insert, a composite with Kevlar that has not been approved by MLB/MLBPA.

Pitchers can use any protective headwear, regardless of whether it has been MLB/MLBPA-tested and approved, as long as it doesn't interfere with play or conflict with licensing agreements.

The big question on Jennings' mind, he said, is why more pitchers seem to be getting hit lately.

"It's scary," he said. "I don't know if hitters are getting more powerful or changing their approach to go up the middle, but I wish someone would come up with an explanation."

"I think the only solution to protect the face [and other areas below the cap line] is a full helmet and mask," Jennings said, "but pitchers need to do too much and I don't see how you can pitch that way."